The present invention relates generally to improving performance of diesel internal combustion engines.
The efficiency of the diesel internal combustion engine is affected by many variables. The horsepower and torque available from an electronic fuel injection, direct injection or natural aspirated, diesel engine are dependent upon the density of the air. Many common gases exhibit behavior very close to that of an ideal gas at ambient temperature and pressure. Charged air-intercooling has a number of important benefits. First, because it provides an additional charge air density increase, it allows the specific output of the engine to be increased. Also as a result of the increased charge density, the altitude capability of the engine is increased and the brake specific fuel consumption is improved. Another major benefit of the charge intercooling is that it reduces the operating temperature of cylinder and exhaust system components. As a result, component durability can be improved while avoiding the need to make these components from more expensive high temperature materials. Perhaps the greatest benefit from charged intercooling is its effect on exhaust emissions. Carbon monoxide and particulate emissions are reduced as a direct result of the increased charge density and air-to-fuel ratio. The effect on NOx emissions can be even more dramatic. The in-cylinder NOx formation reactions are temperature dependent and are controlled by the peak cylinder temperature. Depending on the compression ratio of the engine, a 100 degree Fahrenheit (hereinafter “F” or designated by degrees) reduction in the intake manifold temperature lowers the peak cylinder temperature by 250 to 300 degrees F. and can reduce NOx emissions by 30% or more. Because charge intercooling is one of the few ways to reduce NOx emissions without degrading fuel economy or increasing other emissions, it has become a preferred NOx control technology for turbocharged diesel engines. It should also be noted that the charge air temperature achieved with an air-to-air cooling system varies with the ambient air temperature. As a result, the charge temperature is not as closely controlled as with the Dual Cold Air Induction System (DCAI) where the temperature is kept within fairly narrow limits via thermostatic control. Dual Cold Air Induction System is the most powerful form of charge air-intercooling and can, in theory, achieve charge temperatures below ambient. This system uses R134a refrigerant from the existing truck cooling system to supply the DCAI device.
According to the ideal gas law equation, PV=nRT, wherein P is the pressure of the gas, V is the volume the gas occupies, n is the number of moles of gas present, R is the universal gas constant and T is the temperature of the gas in absolute temperature units, i.e. in Kelvin, a relationship between the pressure, temperature and volume of the gas exists. This relationship indicates that if the gas is colder, it is denser, and denser air will provide more oxygen, allowing a truck to burn more fuel and make more power because denser than normal air-fuel mixtures are more explosive when ignited, resulting in increased power. A common rule of thumb holds that decreasing air intake temperature by 10 degrees F. will increase horsepower and torque by 1%. The converse is also true, a 10 degree rise in intake temperature decreases horsepower and torque by 1%.
In contrast, lower density air means less oxygen, which leads to an increased fuel consumption and less power. Therefore, the composition of the mixture of air and fuel introduced into the combustion chambers of an internal diesel combustion engine significantly affects performance. As such, trucks' and tractors' diesel engine power may be increased by providing a denser than normal air-fuel mixture at the point of ignition. However, to achieve optimum efficiency, the air/fuel mixture must be appropriately maintained at all levels of operation. To address consumer demand for greater engine power, particularly in the diesel internal combustion engines, turbochargers were developed and installed. Turbochargers are devices which utilize mechanical means to increase the pressure of the air-fuel mixture before it enters the combustion chamber of the diesel internal combustion engine.
The process of the compression raises the air-fuel mixture temperature as well as its pressure to above ambient levels. Since the objective is to increase inlet air density, charged air intercoolers (heat exchangers) are often used to cool the air between compressor delivery and the cylinders, so that the pressure increase is achieved with the maximum rise in density. Since the inlet and exhaust pressures are above ambient, more fuel is burned in the engine. The cylinder pressure through the cycle, and particularly during combustion, is substantially higher for turbocharged cycle. The temperature increase associated with the compression degrades volumetric efficiency (i.e., air-fuel mixture per unit volume) by reducing the density of the air-fuel mixture introduced into the combustion chamber.
A number of modifications and enhancements have been made to conventional diesel internal combustion engines in an effort to improve its performance. For example, it is well known that increasing the volume of air and fuel entering the combustion chambers will result in improved performance. Accordingly, to enhance power from an engine it is desirable to cool the ambient intake air before the pressurized air is delivered to the point of ignition. On many trucks and tractors, the first part of the intake tract the incoming air encounters is a tube designed to channel cold air from the grill or inside the fenderwell into the engine. The air then passes into the air cleaner containing an air filter for removing any incoming dirt, insects, and any other contaminants the air might have picked up off the road. The next object the air is likely to encounter is either a turbocharger or engine intake.
A variety of heat exchangers have been developed that attempt to assist in lowering air intake temperatures, including air-to-air coolers and water-air coolers. Traditional heat exchangers transfer heat from a liquid coolant to the atmosphere; intercoolers, however, may also use a gas as a liquid, such as air, as a cooling medium. Intercoolers are installed on diesel engines today and have been known to improve the efficiency and performance of the turbocharged diesel engines for some time. The intercoolers that have been employed to date for these applications have been in a form that is an additional component to the engine, requiring modification to the engine and/or the turbocharger. Therefore, devices have been utilized which introduce into the air/fuel mixture other liquids in an attempt to cool the mixture prior to combustion. There have also been attempts to provide cooling jackets surrounding the air passages through which the air flows prior to entering the combustion chambers.
In contrast to diesel turbocharged engines, naturally aspirated diesel engines draw air directly from the area surrounding the air inlet and filter system. Efforts have been made to improve volumetric efficiency by positioning this air inlet in locations remote to the remainder of the engine. That is, it has been attempted to reduce the ambient air temperature being drawn into the combustion chamber by remotely locating the point at which atmospheric air is collected. Unfortunately, such efforts have yielded only modest gains in volumetric efficiency.
What has been lacking, however, until the present invention, and what the industry long has sought, is a device that optimizes the temperature of an air-fuel mixture at the point of ignition so as to produce maximum horsepower, torque, fuel economy and fewer emissions from a cold air-fuel combination, which includes controlled temperatures of air from the intake air filter and the compressed air prior to the entry of the engine intake.
Therefore, a previously unaddressed need exists in the industry for a new and useful dual cold air induction system, apparatus and method that is capable of delivering a continuous controlled temperature and/or on demand optimally cold air-fuel mixture for greater horsepower, torque, fuel economy, and less emissions. Particularly, there is a significant need for a dual cold air induction system, apparatus and method that produces the lowest temperature of air possible for an air-fuel mixture into the engine intake at the point of ignition so as to produce maximum horsepower, torque, fuel economy and fewer emissions from the dual air fuel charge.